Determination of sharing oil losses using proportional and stratified methods in Krisna field

Abstract

This paper discusses about the oil losses due to emulsion, flash, and mixing oil phenomena that frequently happened in the oil and gas companies. The goals of this work are to calculate the emulsion and vapor correction volumes, shrinkage correction volume of the mixture of two or more crude oils with different densities, and to compare between the common proportional method that usually utilized in petroleum industries and the new proposed stratified method for determining of sharing oil losses. The mixing of crude oils from 7 shippers in Krisna field would be used as a case study, and the equation of API 12.3 was chosen to calculate a shrinkage correction volume. Oils from shippers S1, S2, and S3 were first mixed together in TANK-1 of the 1st station; the mixed oil of TANK-1 was then transported to the next station and stored in the TANK-2 and mixed with other oils from shippers S4 and S5; and finally, the mixed oil of TANK-2 was transported to the final station and stored in the TANK-3 and mixed with other oils from shippers S6 and S7. The proportional method gave almost the same shrinkage correction factor (SCF) for all shippers about 0.20%, while stratified method resulted SCF in between 0.05 and 0.31%. Based on our analysis, more often oil mixes with others its volume would be more decreased. The stratified method is therefore recommended to determine sharing oil losses since it gives a fair result.

Oil Losses Problem in Oil and Gas Industries

“…Just like the name, a liquid will "flashes" or partially evaporates Figure 6. Flash Calculation algorithm [1].…”

“…If the vapor fraction equals 0, the fluid is in liquid phase, if it equals 1, the fluid is in gas phase. Elseif it is in between 0 and 1 (0<n v <1), the fluid is in mixed-liquid-vapor phase; in other words, part of light component in fluid evaporates; this causes oil loss due to flash phenomena [1].…”

“…Calculation procedure of vapor fraction n v [1]. The constants of a, b, c are referenced from PSME of UPN "Veteran" Yogyakarta collaborated with LEMIGAS Jakarta [9].…”

“…Sharing oil losses can be determined with 2 methods, they are Proportional Method, and Stratified Method [1].…”

“…When this occurs, an agreement to determine a fair share of the losses must be made. Hermawan et al [1] have classified oil losses into two categories, they are (1) individual and (2) group losses.…”